The overall goal of this project is to identify new therapies that target influenza virus replication. The global health burden of annual influenza epidemics coupled with the emergence of highly pathogenic strains of influenza virus has highlighted the urgent need for new effective treatments A primary concern with the current drugs (amantadines and neuraminidase inhibitors) used to treat influenza is the development of resistance mutations that negate therapeutic benefit. Published evidence suggests that targeting the influenza virus RNA dependent RNA polymerase (RdRp) is a rational approach for antiviral therapy. The RdRp is responsible for a number of functions including 5'cap recognition, endonuclease activity, replication, transcription, and polyadenylation. Recently, cryo-EM reconstitution studies identified branchedribonucleoproteins (RNPs) structures as putative replication interhiediates and suggested a mechanism for viral replication by a second polymerase activity on the RNP template . The second polymerase activity is believed to be a function ofthe polymerase complex. Clearly, the RdRp provides multiple functional domains that could be targets for antiviral drug therapy. Previous studies showed that mutations in the conserved regions of PB1 subunit of the polymerase complex produce inactive RNA polymerase. We hypothesize that compounds that specifically target the polymerase complex might reduce the frequency of escape mutations, or promote escape mutants that are unfit for replication. We have recently identified potential hit compounds from previous HTS screens that significantly inhibit the influenza virus polymerase activity in an RdRp transient assay. These hit compounds were effective against three different strains of influenza viruses in CPE assays. We propose to characterize these compounds and use high-throughput screening (HTS) of novel small molecule libraries to identify anti-polymerase candidate compounds, chemically optimize them, and establish their effectiveness in an influenza mouse model. \